The present invention is an improvement in the field of fiber optics and more specifically it is a generic technique for mechanically interfacing optical waveguides to bulk media. This invention reduces troublesome optical reflections that occur when an optical waveguide (including optical fibers) is interfaced to a bulk media. This invention can also be used in situations where an optical fiber must be interfaced to other media.
Methods of interfacing fiber optic wave guides to bulk media are well known in the art but the typical methods of using epoxy, or simply end-butting the pieces together, has many complications associated with their use. It is obvious to anyone skilled in the art of fiber optics that it is important to terminate fibers to components with the most reliable and low loss approach. Epoxies remain the industry standard for joining optical fibers to components such as integrated optical circuits (couplers, modulators, etc.), amplifiers, switches, etc. However, epoxies can exhibit a number of undesirable characteristics: 1) relatively high thermal expansion coefficients can cause the fiber to move out of alignment with the component, 2) epoxies change their characteristics over time, including changing refractive index, elasticity, transmissivity, and, adhesion to the parts, 3) all epoxies have relatively low glass-transition temperatures (the temperature at which the epoxy starts to soften), and 4) air bubbles and contamination in the epoxy. Therefore, epoxies have performance and lifetime issues that can affect their suitability for certain applications. Thermal fusing has the potential to overcome the limitations exhibited by epoxies.
Another problem associated with prior art methods is optical reflections due to intervening materials and surface imperfections which cause scatter.
Reflections in fiber optic systems degrade performance. They can lead to temporal dispersion, background noise, losses, crosstalk, laser instabilities, and other problems. Reflections can arise from many sources such as switch and device interfaces, receiver termination, and other connections. Reflection requirements are becoming more and more demanding in such products as dense LAN""s and test equipment. Return loss is one of the most important specifications in many optical devices. Traditional fixes are relatively complex and expensive. For example, a large refractive index discontinuity occurs between an optical fiber and a gradient index (GRIN) lens. This discontinuity can create a return loss of 30 dB. The standard industry method to fix this problem is to angle both the optical fiber and the GRIN lens. This can create a return loss of greater the 50 dB. Using the approach of this invention, with parts that are easy to fabricate and assemble, return losses of greater than 50 dB can be achieved.
The present invention has been made to solve the problems described above. It reduces optical reflections thereby increasing return losses that occur when an optical waveguide, including optical fiber, is interfaced to a bulk media. By thermally fusing the waveguide, or optical fiber, to the bulk media, or to a stand-off which is then attached to the bulk media, optical reflections at the interface are reduced to a minimum due to no intervening materials, elimination of surface imperfections that can cause scatter, and a softening of whatever refractive index discontinuity exists at the wave guide/bulk media or waveguide/stand-off interface due to a slight diffusion of waveguide materials into the stand-off.